When paint is exposed to air, volatile elements of the paint evaporate and an undesirable crust forms. The thickness of the crust increases over time. The crust will form on all exposed paint surfaces including the interior surface of the container and the free surface of the paint. Thus, paint containers must be substantially air tight to protect the paint in the container from being exposed to air.
Known paint containers include a lid for sealing the container. The lid is removed to access the paint and replaced after removing the desired quantity of paint.
A problem with known paint containers is that after a portion of the paint has been used the container will trap an amount of air equal to the volume of used paint. As mentioned above, the trapped air will cause a crust to form on the interior surface of the container and the free surface of the paint. This problem becomes worse as more paint is removed since the volume of trapped air increases.
A further problem with known paint containers is adherence of the lid to the paint container. Paint is often splattered on the lid mating surface when paint is removed from the container. When the lid is thereafter placed on the lid mating surface the paint trapped between the lid and the lid mating surface hardens over time making removal of the lid more difficult. Also, when the lid is replaced on the container, the lid is often re-sealed using a hammer; this often causes paint in the lid mating surface to spray out onto the painter or onto the surrounding support surface.
Yet another problem with known paint containers is the problem of an imperfect seal between the lid mating surface and the lid due to paint drying on the lid mating surface. An imperfect seal allows air to enter into the container and lead to the above-mentioned crust formation. Simply chipping away paint which dries on the lid mating surface is not a solution to this problem since the dried paint is often discolored. If the dried paint is chipped away, some of the chipped paint will inevitably fall back into the container. The discolored paint which falls into the container will change the color of the paint so that paint from the container will no longer match the color of previous paint applications from that same container.
Several known devices for protecting paint in a paint container provide rigid disks which float on the surface of the paint. One such device is disclosed in U.S. Pat. No. 4,625,886 to Eisenman. A problem with devices using rigid floating disks is that the disk must be smaller than the opening to insert the disk into the container. This necessarily leaves an annular space adjacent the interior surface which is exposed to air trapped in the container. A further problem with floating paint protection devices is that they do not address the problem of a crust forming on the inner surface of the container nor do they address the problem of adherence of the lid to the container body.
Another known paint protection device is disclosed in U.S. Pat. No. 2,609,119 to Shilstone. Shilstone discloses a flexible protective cover for preventing the formation of a crust. The protective cover includes a disk and a projecting flange. A problem with Shilstone is that the cover does not protect the entire interior surface of the paint container when the paint level is below the level shown in FIGS. 4-6. Furthermore, Shilstone also does not address the problem of adherence of the lid to the lid mating surface nor the problem of crust formation at the lid mating surface.